Summary: A new UCLA Health analysis indicates that the composition of a child’s gut microbiome at around age 2 may be linked to emotional health years later. Specifically, higher abundances of bacteria in the Clostridiales order and the Lachnospiraceae family were associated with altered connectivity in emotion-related brain networks and with greater risk for anxiety and depressive symptoms by age 7½.
These findings reinforce the importance of the gut-brain axis in early development and suggest that microbial communities in early life could help shape neural circuits that support emotional regulation. The results point to the potential for early preventive strategies—such as targeted diet or probiotic approaches—to reduce the risk of later internalizing symptoms, pending further causal research.
Key Facts
- Gut-brain axis and development: Microbial populations in early childhood appear to influence brain network connectivity tied to emotional processing and mood regulation.
- Predictive microbial patterns: Greater representation of Clostridiales and Lachnospiraceae at age 2 correlated with a higher likelihood of internalizing symptoms (anxiety and depression) in middle childhood.
- Potential interventions: If follow-up studies confirm causal relationships, adjusting the gut microbiome through diet or probiotics could emerge as a preventative or supportive strategy for emotional health.
Source: UCLA
Overview
A study led by researchers at UCLA Health explored associations among early childhood gut microbiome composition, functional brain connectivity, and later emotional symptoms. Published in Nature Communications, the observational study analyzed stool samples collected at age 2, resting-state functional MRI data collected at age 6, and caregiver-reported behavioral assessments at age 7½. The research used statistical tools to identify brain connectivity patterns that linked early microbial profiles with later internalizing symptoms.
The investigators found that microbial profiles characterized by increased Clostridiales and Lachnospiraceae were indirectly associated with higher internalizing symptoms through alterations in connectivity across emotion-related brain networks. The authors emphasize that these results indicate potential programming effects of the early microbiome on neural circuits relevant to emotional health, but that experimental work is needed to determine causality.
Dr. Bridget Callaghan, the study’s senior author, noted the importance of examining how early-life microbial patterns might help shape mental health during the critical school-age years. She and colleagues highlight that if early microbiome differences are confirmed to influence emotional development, interventions that alter microbial composition—such as dietary adjustments or specific probiotics—could be practical options to explore.
Previous pediatric microbiome research has largely focused on infants and toddlers and on outcomes such as motor, language, and cognitive development. This UCLA-led study extends the investigation into school-age mental health by linking microbiome signatures from toddlerhood with brain connectivity and emotional outcomes later in childhood.
The study used data from the Growing Up in Singapore Towards Healthy Outcomes (GUSTO) cohort. From that longitudinal birth cohort, the UCLA team analyzed data from 55 participants for whom stool samples, resting-state MRI, and caregiver reports were available. The analysis first identified combinations of brain network connectivity at age 6 that most strongly correlated with internalizing symptoms at age 7½ and then examined which microbial features at age 2 correlated with those brain connectivity signatures.
The observed link between Clostridiales and Lachnospiraceae populations and internalizing symptoms echoes similar associations reported in adult mental health research. Some species within these groups have previously been implicated in stress response and depression, and they may be particularly sensitive to environmental stressors, which could help explain their relationship with later-emerging emotional symptoms.
The authors advise caution: these results are observational and do not establish causality. Future experimental studies are needed to determine whether the identified microbial groups directly influence brain development and emotional outcomes, and to pinpoint which specific bacterial species are responsible for the associations. Once those species are identified, targeted interventions—dietary changes or probiotics—could be tested as methods to support healthy emotional development.
Co-first authors on the study are Drs. Francesca Querdasi and Jessica Uy, with Dr. Jennifer S. Labus among the contributing authors. The research was conducted in collaboration with institutions including A*STAR’s Institute for Human Development and Potential, KK Women’s and Children’s Hospital, the National University Health System (NUHS), and the National University of Singapore Yong Loo Lin School of Medicine.
Key Questions Answered:
A: Certain bacterial groups are associated with altered communication between brain regions that regulate emotion. Those connectivity patterns are in turn linked to risk for anxiety and depression, suggesting a gut-brain communication pathway that may shape emotional outcomes.
A: Toddlers with relatively higher levels of bacteria from the Clostridiales order and the Lachnospiraceae family were more likely to show internalizing symptoms in middle childhood, with those relationships linked to differences in brain connectivity.
A: Potentially. If future experimental research confirms causal roles for specific bacterial species, interventions such as diet modification or targeted probiotics could be evaluated to support emotional development and reduce risk of anxiety and depression.
About this mental health and neurodevelopment research news
Author: Will Houston ([email protected])
Source: UCLA
Contact: Will Houston – UCLA
Image: The image is credited to Neuroscience News
Original Research: Open access. “Childhood gut microbiome is linked to internalizing symptoms at school age via the functional connectome” by Bridget Callaghan et al., published in Nature Communications. DOI: 10.1038/s41467-025-64988-6
Abstract
Childhood gut microbiome is linked to internalizing symptoms at school age via the functional connectome
The microbiome-gut-brain axis plays a crucial role in mental health, yet studies that directly link microbiome composition to brain function during development are limited. Developmental periods are marked by high neural plasticity and are when many mental health conditions, such as depression and anxiety, first emerge.
In this observational study (N = 55), researchers used sparse partial least squares regression to identify linear combinations of brain network connectivity measures from resting-state fMRI at age 6 that most strongly covaried with internalizing symptoms at age 7½. They then identified microbial abundance profiles from 16S rRNA sequencing of stool samples collected at age 2 that covaried with those brain connectivity signatures. Finally, the team tested whether early microbial profiles were indirectly associated with later internalizing symptoms via the brain connectivity patterns, suggesting possible microbial programming effects.
The study reports that microbes within the Clostridiales order and Lachnospiraceae family are associated with internalizing symptoms in middle childhood through alterations in connectivity within emotion-related brain networks. These results support further investigation into how early-life microbiome composition may shape neural pathways linked to emotional health.